1. Field of the Invention
The present invention relates to feeders for chip components, and in particular relates to a feeder for intermittently feeding chip components in one direction by using the driving force of a chip mounter.
2. Description of the Related Art
Hitherto, a feeder for chip components is known, wherein chip components accommodated in a hopper are dropped one at a time from a discharge hole on the bottom of the hopper onto an endless belt by a vertically moving pipe linked to the operation of a chip mounter while the chip components conveyed to an end portion of the endless belt by intermittently driving the endless belt forwardly by a belt driving mechanism are picked up one by one by the chip mounter (see Japanese Unexamined Patent Application Publication No. 8-48419, for example).
In the above-mentioned feeder, the pipe for dropping chip components in the hopper from the discharge hole is vertically driven by a driving lever pushed down by the chip mounter and the belt driving mechanism drives a belt driving pulley intermittently via a ratchet claw by a driving lever swung by retracting means moving simultaneously with the chip mounter. Since by utilizing the input load of the chip mounter, the chip components are taken out from the hopper onto the belt and the chip components are intermittently conveyed by the belt, the feeder has an advantage that a specific driving source is not required and synchronization between the feeder and the chip mounter can be readily obtained.
Recently, high feeding capacity is required for a feeder of the type and feeders having a capacity of 0.1 s per one chip component or less-have been put to practical use. When chip components are fed in such a short time, jumping and slippage of the chip components occur on the belt, so that a problem that the chip components cannot be fed in a stable state arises. The reasons thereof will be described with reference to FIGS. 1A to 1C.
FIGS. 1A and 1B show an example of operations of the chip mounter and the belt for driving the feeder.
As shown in FIG. 1A, the chip mounter starts to descend at the time t1 and reaches the bottom dead center at the time t2. From the time t2 through the time t3, the chip mounter is stopped while the forefront chip component conveyed on the belt is sucked up. At the time t3, the chip mounter starts to ascend and reaches the top dead center at the time t4. From the time t4 through the time t5, a suction nozzle is moved and orientation of the chip component is recognized, so that the sucked chip component is mounted on a circuit board, etc.
On the other hand, as shown in FIG. 1B, since the belt is driven in synchronization with the ascent of the chip mounter, the belt is forwardly driven only during the ascent of the chip mounter xcex94ta (t3 to t4) and is stopping for the rest of the time.
In such a high-speed operation having a tact time of 0.1 s as described above, the belt driving time xcex94ta is to be smaller in proportion to the tact time. Therefore, the belt has to be driven at a high-speed, so that the frictional force between the chip component and the belt is not effectively exerted, and the chip components cannot be thereby fed in a stable state due to jumping and slippage of the chip components on the belt.
Accordingly, it is an object of the present invention to provide a feeder for chip components capable of feeding chip components in a stable state even in the high-speed operation by driving a conveying section at a lower speed than that of the chip mounter and even when the chip mounter is stopped.
In order to achieve the above-mentioned object, in accordance with a first aspect of the present invention, there is provided a feeder for chip components, including a feed lever operated according to the input load from a chip mounter and a conveyor belt connected to the feed lever via a one-way feeding mechanism, the feeder feeding chip components on the conveyor belt in one direction by intermittently driving the conveyor belt in one direction, the feeder for chip components comprising: an urging means for urging the feed lever in the returning direction by storing the input load of the chip mounter in the operating direction as energy; and a delay mechanism for delaying the returning operation of the feed lever relative to the operation of the chip mounter in the returning direction, wherein when the chip mounter operates in the operating direction, the feed lever is moved in the operating direction by linking to the chip mounter while the conveyor belt is maintained in a stationary state by the one-way feeding mechanism, and wherein when the chip mounter operates in the returning direction, the feed lever is moved in the returning direction so as to be delayed relative to the chip mounter by the urging means and the delay mechanism while the conveyor belt is driven via the one-way feeding mechanism.
The feeder for chip components according to the first aspect of the present invention will be described with reference to FIG. 1C.
In the feeder, when the chip mounter operates (t1 to t2), the belt is stopped, and when the chip mounter is retracted (t3 to t4), the belt is driven; however, the belt is out of synchronization with the retraction of the chip mounter due to a delay mechanism and continues to be driven at a low speed even after the chip mounter reaches the top dead center. Therefore, the belt driving time xcex94tb (t3 to t6) can be prolonged compared with the conventional driving time xcex94ta (t3 to t4), so that the belt can be driven at a lower speed for the same feeding amount. Thereby, the frictional force between the belt and the chip components are effectively exerted and the chip components can be supplied with high stability even in high-speed operation.
In particular, in the feeder, the belt is not driven by the input load of the chip mounter but when the chip mounter is retracted, driven by the energy stored in the urging means. Therefore, the belt can be driven at a low speed without being restricted by the operation of the chip mounter.
The belt drive termination time t6 may be any time as long as it is before the next ascent starting time t5 of the chip mounter, so that the belt driving time can be secured as long as possible within the time range of t3 to t5. The operating speed of the belt is adjustable by the delay mechanism.
As a delay mechanism, a known delay mechanism such as an eddy current damper, a damper utilizing viscosity of a fluid, and an air damper can be employed. The set-up place for the delay mechanism is not limited to the feed lever portion; it may be arranged around the one-way feeding mechanism or a driving unit for the belt.
As operating characteristics of the delay mechanism, the resistance force may be exerted in both operating and returning directions of the feed lever, or it may be exerted only in the returning direction while it is not exerted in operating direction.
As the urging means, means for storing elastic energy such as a spring and means for storing potential energy such as a weight may be used.
In a second aspect of the present invention, a reciprocating conveying member is used instead of the belt in the first aspect. That is, in accordance with the second aspect, there is provided a feeder for chip components, including a feed lever operated according to the input load from a chip mounter and a conveying member connected to the feed lever via a transmission mechanism, the feeder feeding chip components on the conveying member in one direction by reciprocating the conveying member using a frictional force, the feeder for chip components comprising: an urging means for urging the feed lever in the returning direction by storing the input load of the chip mounter in the operating direction as energy; and a delay mechanism for delaying the returning operation of the feed lever relative to the operation of the chip mounter in the returning direction, wherein when the chip mounter operates in the operating direction, the feed lever is moved in the operating direction by linking to the chip mounter while the chip components are slid relative to the conveying member by retracting the conveying member at high speed via the transmission mechanism, and wherein when the chip mounter operates in the returning direction, the feed lever is moved in the returning direction so as to be delayed relative to the chip mounter by the delay mechanism while the chip components are unitarily conveyed with the conveying member by forwardly driving the conveying member at low speed via the transmission mechanism.
When the chip mounter operates in the operating direction, and accordingly, the feed lever is moved, the conveying member is retracted via a transmission mechanism in a high speed. Thereby, the frictional force is scarcely exerted to the chip components on the conveying member so that only the conveying member is retracted while the chip components maintain their positions. Next, when the chip mounter operates in the returning direction, the feed lever is retracted behind the chip mounter due to the delay mechanism. Therefore, the conveying member connected thereto via the transmission mechanism also proceeds at a low speed behind the chip mounter. Accordingly, the frictional force is exerted to the chip components on the conveying member, so that the chip components also proceed unitarily with the conveying member.
Due to the delay mechanism, the proceeding time of the conveying member can be prolonged until the time just before the next operation starting time of the chip mounter, so that the driving time of the conveying member can be secured as long as possible. Therefore, the conveying member can be driven forwardly at a low speed, so that the chip components can be supplied with high stability even in high-speed operation.
Preferably, the transmission mechanism comprises a cam intermittently rotating in one direction according to the movement of the feed lever and a spring for making the conveying member contact with and to track the surface of the cam. With these features, when the chip mounter operates in the operating direction, the cam is rotated via the feed lever, so that the conveying member is dropped into the valley portion of the cam from the peak portion thereof. Thereby, the conveying member is retracted at a high speed. When the chip mounter operates in the returning direction, the conveying member rides onto the peak portion from the valley portion of the cam, and thereby the conveying member proceeds at a low speed. The proceeding speed of the conveying member is reduced by functions of the cam profile and the delay mechanism, so that the frictional force between the conveying member and the chip components is sufficiently exerted, resulting in supplying the chip components without slippage.
Preferably, the transmission mechanism comprises a bell crank wherein the feed lever and the conveying member are rotatably connected to arm portions projectingly formed on both sides of a swinging shaft. With these features, when the feed lever and the conveying member are connected together via the bell crank, the feed lever and the conveying member are operated in synchronization with each other. At this time, the conveying member can be retracted at a high speed and moved forwardly at a low speed by operating the feed lever at a high speed in the operating direction and at a low speed in the returning direction due to the delay mechanism.
Preferably, the delay mechanism is an eddy current damper. In the eddy current damper, as is generally known, a conductive member is arranged so as to oppose magnetic flux generating means (a magnet, for example) and one of the magnetic flux generating means and the conductive member is movable relative to the other in the direction orthogonal to the opposing direction. Since an eddy current induced in the conductive member is generated in the direction that prevents changes in magnetic flux, a resistance force is exerted to the movable member by the eddy current and with increasing displacing speed of the movable member, the lager resistance force is exerted. That is, the load proportional to the speed is obtained from the eddy current damper, so that the acceleration is stopped at the speed determined by the relation with the spring force. Therefore, in high-speed operation, conveying can be securely achieved. For example, when the eddy current damper is arranged between the feed lever and a fixed portion, if the feed lever moves in any direction, the resistance force is exerted to the feed lever so as to prevent the movement in the direction. Since the driving force for the feed lever in the operating direction is given by the chip mounter, even when the resistance force is exerted, the feed lever is unitarily moved with the chip mounter without being prevented by the resistance force. In contrast, since the driving force for the feed lever in the returning direction is given by the urging means, the urging force by the urging means is restrained by the eddy current damper, so that the feed lever can be returned at a low speed. Since the eddy current damper has not sliding portions, it has an advantage that characteristics do not change even when using for a long period.
Preferably, the delay mechanism is a hysteresis brake. The hysteresis brake comprises composite magnetic poles having the N pole of the magnet and the S pole alternately arrayed and a magnetic material arranged so as to oppose the composite magnetic poles and being relatively movable in the direction orthogonal to the opposing direction, and generates a brake force utilizing the hysteresis loss of the magnetic material. Different from the eddy current damper, the brake force of the hysteresis brake is not dependent on the speed and the hysteresis brake has an advantage that the brake force can be readily obtained even in low-speed operation. When the hysteresis brake is arranged between the feed lever and a fixed portion, for example, the sufficient brake force can be obtained even in low-speed operation of the feed lever, and delay operation can be securely performed. In addition, since the hysteresis brake also has not sliding portions, characteristics thereof do not change even when using for a long period.
Preferably, the hysteresis brake adds a function as an eddy current damper by forming the entirety of or part of the magnetic material forming the hysteresis brake from a conductive material. The hysteresis brake is not dependent on the speed as described above, and when it is used as a simple substance, the feed lever continues acceleration, so that the speed control and the restriction of generation of a shock and a noise at the top dead center may be difficult. Therefore, by adding a function as an eddy current damper to the hysteresis brake, the chip components can be supplied with high stability for all the operations from the low-speed to the high-speed.